A mechanism for reversible mesoscopic aggregation in liquid solutions.

Area of Science:

• Physical Chemistry
• Materials Science
• Biophysics

Background:

• Solutions often display unexpected liquid inclusions of solute-rich phases.
• The mesoscopic size of these inclusions challenges current theories of heterophase fluctuations.

Purpose of the Study:

• To elucidate a microscopic mechanism for the nucleation of metastable solute-rich liquid phases in solutions.
• To explain the formation and evolution of mesoscopic inclusions outside thermodynamic stability.

Main Methods:

• Theoretical modeling of nucleation and growth processes.
• Analysis of molecular complex formation and its impact on phase stability.
• Investigation of droplet dynamics, including mechanical instability and pressure changes.

Main Results:

• A non-classical nucleation mechanism is proposed, dependent on the formation of long-lived solute complexes.
• Nucleated droplets grow until mechanical instability arises due to reduced internal pressure.
• The ensemble of droplets reaches a steady state, with initial evolution resembling Ostwald ripening.

Conclusions:

• The study provides a microscopic explanation for the formation of metastable liquid inclusions in solutions.
• Molecular complexation is identified as a key factor enabling nucleation outside stable phase regions.
• Droplet growth and instability dynamics are linked to the metastability of the solute-rich phase.